The present invention relates to a novel light-sensitive element and a process for preparation thereof, and more specifically to a light-sensitive element by which images having high sensitivity and high resolution can be obtained with a simple treatment after imagewise exposure.
A light-sensitive element which comprises a photopolymerizable composition on a substrate is known in the field of imaging, resists, printing plate and the like. The photopolymerizable composition comprises an organic polymer binder, an ethylenically unsaturated compound, a photopolymerization initiator and additives which improve properties of the composition. Recently, microcapsulated light-sensitive compositions have been used in photopolymerizable elements, concerning which a number of patent applications are publicly disclosed. U.S. Pat. Nos. 4,399,209, 4,440,846, 4,416,966 and 4,501,809, Japanese unexamined patent publications (hereinafter referred to as J.P. KOKAI) No. Sho 59-30537, Sho 57-124343, Sho 57-179836, Sho 57-197538, Sho 59-91438 and Sho 61-275742, and Japanese examined patent publication (hereinafter referred to as J.P. KOKOKU) No. Sho 42-14344 are directed to imaging processes in which microcapsulated light-sensitive compositions are used. A light-sensitive element used in the imaging process is prepared by microcapsuling a liquid photopolymerizable composition and at least one of a color producing reagent and a developer which react with each other to produce a colored compound and then applying the resulting microcapsules on a substrate. When both of a color producing reagent and a developer are applied on a substrate, microcapsulation prevents contact of the color producing reagent with the developer by the walls of microcapsules so that the light-sensitive element keeps good storage stability. By pattern exposure, exposed areas are cured while unexposed areas are not cured. The microcapsules in the unexposed areas are destroyed by any energy so that the color producing reagent gets contact with the developer to produce a colored compound, which results in producing images.
U.S. Pat. Nos. 4,636,453, 4,687,725 and 4,916,041, J.P. KOKAI No. Sho 58-224752, Sho 59-2845, Sho 61-281242, Sho 61-135793 and Sho 62-250455 are directed to printing plates which comprise a microcapsulated light-sensitive composition. U.S. Pat. No. 4,636,453 discloses a photopolymerizable element which is prepared by encapsulating at least one active component having compatibility with other components of a photopolymerizable composition in pressure-destructable microcapsules having resistance to a solvent for the photopolymerizable composition, applying on a susbstrate the resulting microcapsules together with the other components of the photopolymerizable composition and applying a protective layer thereon. U.S. Pat. No. 4,636,453 is directed to a presensitized plate which keeps strorage stability by microcapsuling components of a photopolymerizable composition to isolate the components from each other. The plate is pressed under sufficient pressure to destroy substantially all of the microcapsules prior to use, then imagewise exposed to light and developed with a solvent which dissolves the photopolymerizable layer to remove the unexposed areas completely. U.S. Pat. No. 4,687,725 discloses a light-sensitive element which comprises microcapsules containing a photo-setting composition on an etchable layer. After the light-sensitive element is imagewise exposed to light, the microcapsules are destroyed to form an etching resistive layer with the photo-setting composition running off from the destroyed microcapsules in the unexposed areas. In subsequent etching, an etching solution can soak easily through the microcapsule layer in the exposed areas to etch the underlying layer because the microcapsule layer in the exposed areas is porous, which results in formation of a pattern. U.S. Pat. No. 4,916,041 discloses a printing plate which can be obtained by imagewise exposing to light a presensitized plate which comprises a hydrophilic substrate and a highly light-sensitive layer applied thereon which comprises a hydrophilic binder and hydrophobic microcapsules comprising silver halide, a reducing agent and ethylenically unsaturated compound, destroying the unexposed microcapsules to run off the composition therein, photo-setting the runned-off composition and washing off the exposed microcapsules. J.P. KOKAI No. Sho 58-224752 discloses a printing plate which can be obtained by imagewise exposing to light a light-sensitive layer which comprises hydrophilic microcapsules containing a photo-setting resin applied on a water-resistant substrate, destroying the unexposed microcapsules to run off the composition therein and photo-setting the runned-off composition. J.P. KOKAI No. Sho 61-281242 discloses a process for preparing a printing plate comprising the steps of imagewise exposing to light a light-sensitive element comprising a substrate having provided thereon microcapsules containing photopolymerizable monomers, laying the light-sensitive element on the top of a hydrophilic substrate to press together, transferring the photopolymerizable monomers in the microcapsules in the unexposed areas to the hydrophilic substrate and exposing the substrate to light over the whole surface thereof. J.P. KOKAI No. Sho 62-250455 discloses a printing plate which can be obtained by imagewise exposing to light a light-sensitive element comprising a hydrophilic substrate having provided thereon a light sensitive layer containing a hydrophilic binder and microcapsules comprising photopolymerizable monomers and a hydrophobic wall membrane, destroying the unexposed microcapsules by heating to run off the composition therein, photo-setting the runned-off composition and subsequently removing the exposed areas of the light-sensitive layer.
From the above, it is necessary in the prior art to incorporate a light-sensitive composition in a microcapsule and to destroy the microcapsule prior to or after imagewise exposure to exhibit the function of the composition.
Since the above mentioned photopolymerizable elements which comprise microcapsules need the steps of destroying the microcapsules, transferring the composition in the microcapsules to another substrate, post exposing the resulting substrate and the like, such complicated steps increase the cost for the treatment.
Further, U.S. Pat. No. 4,636,453 discloses use of a solvent to remove the uncured areas after exposure to light, which is not preferred in view of preservation of the environment and health.